Hitherto, several patents have disclosed methods for binding active ingredients to ion-exchange resins. For example, active ingredients are immobilized to cationic or anionic polystyrene-divinyl benzene resins, as described in British Patent No. 857,193. Several other patents also describe methods for coating active ingredient/resin complexes. For example, U.S. Pat. No. 3,138,525 discloses a method for concealing the taste of amprotopine by forming a complex with a cationic resin and coating it with wax. Also, British Patent No. 1,218,102 describes a method for coating with a device such as an air-fluidized bed, a complex in which a cationic active ingredient is immobilized to an anionic resin. Further, Japanese Patent Application Laid-Open Gazette No. Hei 3-52824 describes a sustainedly releasing medicine capable of regulating the release rate of an active ingredient, which medicine comprises an active ingredient/ion-exchange resin complex coated with an ionic polymer having the polarity opposite to that of the resin.